The present invention relates to a lubricant supply system for a scroll fluid machine such as a compressor, an expander or a liquid pump.
A scroll compressor of the type in which a drive shaft is supported at both sides of an electric motor is disclosed in Japanese Patent Unexamined Publication No. 62-135676. In this known scroll compressor, the bearing mounted on a lower suspension structure of the compressor to support the lower portion of the drive shaft is lubricated with a part of lubricant which is suctioned by a pumping action effected by rotation of the drive shaft from a lubricant reservoir through a lubricant passage bore and then supplied to the bearing via lubricant supply holes formed in an inner race of the bearing past a passage hole and a peripheral groove. The remainder of the lubricant is supplied to the other bearing and other portions requiring lubrication.
Thus, in this lubricant supply system, the smoothness of the flow of the lubricant tends to be impaired due to the fact that a part of the lubricant is supplied to the bearing provided on the lower structure while the remainder is fed to the other bearing and other portions.
In addition, the lubricant supply system is required to have a complicated structure in order to distribute the lubricant to the bearings at rates which are optimum for the respective bearings.
Furthermore, this known lubricant supply system may fail to create the necessary supply pressure when the pumping effect is too low due to a low rotation speed of the drive shaft, particularly in the case where the operation speed of the rotary compressor is controlled by an inverter.